1. Field of the Invention
The present invention relates to an optical output system, more particularly, an optical output system with auto optical power control for an optical mouse.
2. Description of the Related Art
Referring to FIG. 3, it shows a conventional optical output system 30 for an optical mouse. The conventional optical output system 30 comprises: a light emitting device 31 and a driver 32. The light emitting device 31 is used for generating emitting light. The driver 32 is used for driving the light emitting device 31. At present, the light emitting device 31 is a laser diode for outputting laser light. For safety demand and stable resolution, the output power of the laser light must be controlled to a predetermined value, for example below 1 mW. Therefore, the manufacturer must adjust the driver 32 to obtain the predetermined value of the output power.
Nevertheless, the output power may still be unstable owing to the following reasons:    1. variation of the laser diode (Die-to-Die variation on the laser diode output power under a fixed driving current);    2. variation of the driving current (voltage) source of the laser diode (Die-to-Die driving current variation, Vdd dependence and temperature dependence);    3. temperature dependence of efficiency for transforming electrical power to optical power in the laser diode; and    4. mouse-to-mouse variation of the optical output system in the optical mouse.Besides, when the output power is adjusted to suit a specific reflective surface assumed by the manufacturer, the optical mouse may not work on another reflective surface. That is, a conventional optical mouse cannot be utilized for all reflective surfaces.
Therefore, it is necessary to provide an optical output system so as to solve the above problem.